In the manufacture of electric motors, particularly for use in the air moving industry, it is desirable to utilize self-aligning bearings in order to control alignment of the parts and provide the desired air gap between the stator and rotor.
One common type of bearing that has been used is known as a sleeve bearing which utilizes a spherical seat against which a spherical bearing is urged by a spring. Do to the wide range of horsepower outputs in a multiple speed motor, it is necessary to provide sufficient spring force to hold the self-aligning bearing in place under load ranges of two to 300%. The spring forces act in two directions in that the low horsepower starting is adversely affected when the spring forces are increased to handle heavy loads. The problem is further compounded when normal manufacturing tolerances add to the displacement of the assembled spring to the bearing. Further, the use of a coil spring in an effort to reduce the effective assembly tolerance interferes with the use of wicking materials and the automated assembly of the motor.
In U.S. Pat. Nos. 3,966,278 and 4,090,749 an electric motor is shown with self-aligning bearings wherein the end member is formed with an enlarged opening and a bearing seat is defined by radially inwardly extending portions. A high-rate spring is inserted and has a central annular portion for engaging the bearing.
Such an arrangement necessitates that the end member be made with a very large opening and is difficult to assemble. Where the end member is die cast, complex cores are required. In addition, the large opening precludes the use of conventional standard motor mounting structures.
Accordingly, among the objectives of the present invention are to provide an electric motor with a self-aligning bearing that incorporates close dimensional tolerances and eliminates normal die cast tolerances; which minimizes variation in starting torques; which provides unobstructed channels for ease of assembly of oil reservoir material; which permits variation in the holding forces by simple techniques during manufacture and which utilizes a standard size external hub permitting a conventional mounting system to be used.
In accordance with the invention, the electric motor comprises a casing, a stator mounted in the casing, a rotor, and end members rotatably mounting the rotor with respect to the stator. The end members are die cast and comprise an integral hub having a plurality of radially inwardly extending portions defining a bearing seat, a plurality of axially extending ribs on the inner surface of the hub having slots machined therein defining a surface in each rib that is accurately spaced axially with respect to the seat. A substantially flat spring member is positioned so that its annular periphery engages the surfaces and has radially inwardly extending fingers engaging the bearing.